Hot power from Betapack 3?

[Biskit]

Hi All,

 

I suspect you may have guessed from the title what this post is about... and I know the immediate advice will be "don't use dimmers set to 100% for items requiring hot power, especially things with ballasts, discharge lamps etc", however...

 

Can anyone comment on this specifically using modern dimmers (Betapack 3s in this case) which have on-board manual digital controls (and hence could reliably be set to fixed 100% output without relying on external control). After all, Anytronics Contractor series dimmer channels can be set to switching functionality only, and in this mode they work quite hapily with inductive loads. Having worked on these, I know they still use the thyristors even when operating in this way. And these are older technology than a Betapack 3.

 

I have a show in a venue next week which does not have dedicated hot-power available at the patch, and there are no local 13A outlets anywhere useful. I need to get power to 8 mac 250s. I can afford to lose 6 dimmer channels in order to get around this problem if necessary, setting one rack (Betapack 3) manually to 100% on all channels, disconnecting the DMX and using the output MCBs to switch. Not ideal, but a makeshift one-off solution? Or potentially dangerous for the macs/dimmer?

 

Running mains up to the rig or patch pannel from the nearest 13A outlets is undesirable for several reasons (nasty cable runs, and sharing the ring-main with the bar being the most obvious). Tailing power in to the dimmer supply feed is also awkward as we don't have the required distro.

 

Any comments greatly appreciated!

 

Thanks,

 

Ben.

[David A]

I wouldn't put my mac 250s on dimmers, not worried about the dimmers but the macs.If you have a technically competent person around I would suggest you short out the triacs for your show then remove the links afterwards.

[Tomo]

In general, most good quality modern SCR dimmers can happily drive all kinds of nasty loads.

 

However, even when set at 100%, they all affect the waveform that comes out - there is a slight 'blip' around the zero-crossing point where the triac turned off but didn't yet turn back on again in the other direction.

 

In general, the cheaper the dimmer, the worse this is.

 

Intelligent fixtures (moving lights, scroller PSUs etc) rather dislike this, and some could even be damaged by it.

 

However, many modern PSUs inside these units can cope, so most modern fixtures on good quality dimmers are likely to be ok.

 

But I'd still prefer not to do it - it's much better to drive them from true 'hot power', or via a relay.

[lightjocky]

I have the chilli pack jr in my school that also have a "hot power function" by pressing the test button you can select power to 100% however after a while the dimmer clicks out and the test function finishes is this the idea you are using or are the betapack different if not bare this in mind and dont do it !

 

lightjocky

[Ekij]

Whats the power going into the Betapack3?

Somewhere upstream of the Betapack3 there has to be a plug/socket or a breaker and this seems the preferable point to hook up your (temporary) hard power from.

[AndyJones]

I'd rather plug into a local non dim or 16a and keep the dimmer channel!

[peternewman]

I have the chilli pack jr in my school that also have a "hot power function" by pressing the test button you can select power to 100%

Lightjockey I don't know about these dimmers in particular, but it's highly likely, especially as you mention a test button, that this function is just for flashing out. To allow you to put the dimmer channel at full without using the desk. In which case make sure you read and digest what Tomo said, as it's generally not a good idea.

[Jivemaster]

Most kit prefers a clean sine wave supply. Most dimmers set to ON provide a waveform with a glitch at the zero crossing point. You may get away with running MACs of a dimmer, BUT the first failure will be more expensive than getting a betapack disconnected and a hard distro put in.

 

One of the real NASTIES is the little mirror-ball motor. A little load -about 20 watts but very inductive and one will kill a 10a dimmer.

[paulears]

I must have been very lucky then.... Our old STMs which pop at the mere hint of anything odd being plugged into them are, and always have been perfectly happy with mirror ball loads - it's a tiny device, physically - very little copper. I guess the windings do present an inductive load - but I'd never given much thought to actually how much? Flu fittngs for the UVs don't cause any snags either - what dimmers are you destroying?

[David A]

A mirror ball motor will not and cannot blow a dimmer, this is wrong information.My original suggestion to short out the triacs is simple and avoids any potential problems with waveform.

[b1nuzz]

Whats the power going into the Betapack3?

 

We seem to have brushed past this comment.

 

Surely if you are happy to lose the dimmer channels, why not lose the actual dimmer.

 

Use the socket that the dimmer is in to power a distro, then use the distro to power your movers.

 

I know you said in your post that you dont have a distro, but a simple 'square D' distro will only set you back about £30 ish for a week, and that will be alot cheaper than repairing a broken betapack.

[Tomo]

Use the socket that the dimmer is in to power a distro, then use the distro to power your movers.

 

I know you said in your post that you dont have a distro, but a simple 'square D' distro will only set you back about £30 ish for a week, and that will be alot cheaper than repairing a broken betapack.

Indeed - especially as the thing that's most likely to die when run from dimmer-supplied power is the moving light.

 

And those are really, really expensive to fix.

[Ike]

Would there really be much risk? I could just be being thick but I would have thought a movers power supply (presumable switching) would be at less risk from non sine waves than a big lump of iron?

[Tomo]

Would there really be much risk? I could just be being thick but I would have thought a movers power supply (presumable switching) would be at less risk from non sine waves than a big lump of iron?

It essentially depends on the assumptions made by the manufacturer.

If these assumptions turn out not to be true then Bad Things can happen.

 

And most manufacturers assume that the inbound power is more-or-less a sinewave.

[Ynot]

Couple of things to consider here.

 

The manuals will most likely state categorically that dimmed power must not be used - the Martin books certainly do.

Going against mfr recommendations is a quick way to losing ALL service/support.

 

Then there's the fact that many discharge lamps pull a short duration high current spike which will exceed the rating of the fuse, but not blow it as those are delayed action protective devices. That MAY not be the case with the fuses/trips in dimmer packs.

 

At the end of the day, it doesn't cost a lot to hire in a small distro and whatever adaptors you need to do the job properly, so why not just do that????